The Open Mobile Alliance Device Management (OMA DM) specification refers to a protocol of managing a user equipment in a mobile communication network by a remote server. A user equipment in compliance with the OMA DM specification shall be provided with a device management tree which is a tree-like data structure. The device management tree of the user equipment is an interface via which a Device Management Server (DMS) manages the user equipment in the Device Management (DM) protocol, and a Device Management Agent (DMA) of the user equipment is configured to interpret and execute various management commands issued from the DMS.
Management Objects (MOs) available to the user equipment are stored as nodes in the device management tree, each of which is addressable with a unique Uniform Resource Identifier (URI), and the DMS manages each node in the device management tree for the purpose of controlling resources of the user equipment. As illustrated in FIG. 1 which is a schematic diagram of a device management tree, the device management tree includes a requisite root node and nodes attached to the root node, which may be divided into internal and leaf nodes by their locations, where the leaf node may be attached to the internal node. The nodes of the device management tree describe the resources of the user equipment, e.g., a Device Management Account (DMAcc), a Ring signal, a Screen Saver, an Operator, an International Mobile Subscriber Identifier (IMSI), a Vendor, various applications, etc. The nodes in the device management tree may be divided into permanent and dynamic nodes by their operability, where the permanent node refers to a node which can not be generated and deleted by the DMS in operation, e.g., a node built in the user equipment by a device vendor, and the dynamic node refers to a node allowable to be generated and deleted dynamically by the DMS in operation.
For convenient management of the DMS on the user equipment, the OMA DM specification defines a Device Description Framework (DDF) to indicate information on hierarchical relationships between, URIs and attributes, etc., of the MOs in the device management tree, which is stored in the form of a DDF document in the user equipment. Since the DMS knows the information on each node in the device management tree of the user equipment from the DDF document of the user equipment, the DMS shall store locally the DDF document of the user equipment in order to manage the user equipment.
In the prior art, the DDF document of the user equipment typically is retrieved from the user equipment and stored locally by the DMS in advance. The inventors have identified that during management of the DMS on the user equipment, if the device management tree of the user equipment is structurally changed, particularly due to a behavior local to the user equipment, for example, where a user adds or removes a piece of software or attachment to or from the user equipment, etc., then the user equipment can not report the structural change of the device management tree to the DMS so that the DMS can not update in synchronization the locally stored DDF document according to the structural change of the device management tree but instead may manage the user equipment still based on the locally pre-stored DDF document, thus resulting in a failure of the DMS to address or otherwise manage properly any management object changed in the user equipment and consequently degrading effective management of the DMS on the user equipment.